Embodiments of the present invention relate to a support electrostatic chuck for holding a substrate in a process chamber.
In the processing of substrates, such as semiconducting wafers and displays, a substrate is placed on a substrate support in a process chamber. The support can include an electrostatic chuck having electrodes capable of being electrically biased to hold the substrate on the support. The electrodes may also be powered with high frequency electrical power to energize a process gas in the chamber to process the substrate. The support can also comprise a support post and pedestal that supports the electrostatic chuck in the chamber, and may be capable of raising or lowering the height of the chuck and substrate. The support post and pedestal can also provide a protective enclosure for connecting wires, gas tubes etc, that connect to portions of the support.
In a typical chamber process, the energized process gas is used to process a substrate by, for example, etching or depositing material on the substrate or to clean surfaces in the chamber. The energized gas can have highly corrosive species which etch away exposed portions of the support, as well as ionic and radical species energized with kinetic energy which bombard the exposed support portions to erode them. The eroded support is typically replaced after a number of process cycles and before it provides inconsistent or undesirable electrical properties for holding substrates or for generating the plasma. Also, particles eroded away from the support can contaminate substrates being held on the support and so such erosion is undesirable.
Substrate supports, which provide better resistance to erosion by the energized gas, include electrostatic chucks made of ceramics, such as aluminum nitride, which have an embedded electrode. The ceramic chuck is brazed to an underlying stainless steel pedestal, as described for example in commonly assigned U.S. Pat. No. 6,563,686 to Tsai et al. and U.S. Pat. No. 6,853,533 to Parkhe, both of which are herein incorporated by reference in their entireties. Ceramic chucks provide improved resistance to corrosion by energized process gases and maintain their structural integrity at high temperatures.
However, one problem with ceramic chucks arises due to the thermal expansion mismatch between the ceramic and the supporting pedestal which is typically made from metal, especially at high processing temperatures. The difference in thermal expansion coefficients result in thermal and mechanical stresses, which can cause the ceramic to fracture or chip. One solution to this problem is described in commonly assigned U.S. Patent Publication No. 2002/0036881 to Shamouilian et al, filed on May 7, 1999, now abandoned, which is also herein incorporated by reference in its entirety. The support described by Shamouilian et al. has a ceramic electrostatic member having an electrode that is joined to a base beneath the electrostatic member. The base is made of a composite of a ceramic and a metal, which has a coefficient of thermal expansion that is sufficiently close to that of the ceramic e-chuck to reduce thermal expansion stresses. The ceramic e-chuck and base are typically brazed together to provide a strong bond between them. The base in turn is joined to an underlying support via a metal bond.
However, such substrate supports still get eroded with time in the chamber and replacement of the entire e-chuck electrostatic chuck is costly. The entire e-chuck electrostatic chuck has to be replaced because its component parts are integrally attached to one another. Also, when replacing the e-chuck electrostatic chuck, the operator often damages the electrostatic chuck or portions of the electrostatic chuck due to improper alignment of the e-chuck electrostatic chuck with various connectors and tubing in the chamber. Improper connections can also result in subsequent processing problems, for example, the helium gas supplied to the e-chuck electrostatic chuck can also leak out if the helium gas tubes and junction holes are improperly aligned.
Thus, it is desirable to have a substrate support that exhibits reduced thermal expansion mismatch and is tolerant to erosion in the chamber environment. It is also desirable to be able to easily replace the substrate support and at lower costs. It is further desirable not to have to replace the entire electrostatic chuck as frequently as necessary with conventional supports. It is also desirable to have a support that can be replaced without damaging components or portions of the electrostatic chuck.